Individuals are increasingly spending more time using mobile devices and less time using traditional computers. This shift in usage is present in both personal and in business contexts, and presents ongoing challenges. For example, employees of companies are increasingly using mobile devices, and in particular, mobile applications, in their work-related activities. Unfortunately, existing approaches to protecting computers and to enforcing computing-related policies are not necessarily suitable for use with mobile devices. As one example, firewalls and other security devices typically enforce policies against network traffic based on a set of rules. Requests to access content are rejected or allowed based on a classification of that content (e.g., as “pornography” or “business”). Unfortunately, mobile devices often access resources for which traditional classification techniques are inapplicable or inefficient.